Cytochrome P450 is an enzyme involved in the detoxification process. The bacterial enzyme has been purified to homogeneity and runs as a 100 kDa protein on SDS-PAA gels. Dr. Black and co-workers have been able to obtain small three-dimensional crystals which are not sufficiently large for x-ray crystallographic analysis. Ultracentrifugation experiments have indicated an unusual axial ratio of 7:1 for this molecule. To facilitate any structural work and to verify the axial ratio, Dr. Black visited our lab to investigate the protein by electron cryo-microscopy. Preliminary images seem to support the model of an elongated shape. In addition, this water-soluble protein is known to interact with lipids, perhaps as an peripheral membrane protein. Experiments have therefore been started to crystallize the cytochrome P450 on lipid monolayers.